1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
2. Description of the Related Art
The reduced size and increased integration level of semiconductor devices have made it more important to accurately form patterns of desired sizes.
However, a reduction in pattern size may result in an optical proximity effect (OPE), which prevents photoresist patterns of desired dimensions from being faithfully formed. For example, an isolated line and a dense line (or isolated line and isolated space) having the same line width on a photomask may have different line widths on photoresist patterns. Thus, for an actual photomask, mask patterns are subjected to an optical proximity correction (OPC) to obtain photoresist patterns of desired dimensions.
However, even a photomask subjected to the optical proximity correction may make the photoresist patterns deviate from the desired dimensions. A possible cause is a temporal change in a factor contributing to the optical proximity effect. Another possible cause is a variation in the factor contributing to the optical proximity effect among exposure apparatuses.
Much effort has been made to develop immersion exposure as a technique for improving the resolution of photolithography. The immersion exposure involves carrying out exposure with a liquid such as water interposed between a projection lens and a substrate (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 6-124873). The immersion exposure may also be involved in the above problem, and an effective solution has been desired.